Large dragline excavating machines are typically supported on stationary tubs during excavating operations of the excavating machines. The stresses created by the weight of the excavating machines and their excavating movements place large forces on the tubs requiring the tubs to be correspondingly large in size and strength. Larger excavating machines also are movable from one location to another by walking mechanisms which lift the machine up and move it forward in a walking type movement. During each walking step, the tub is picked up by the frame of the machine and moved with the machine. Such lifting movement also requires that the tub be of high strength to withstand the forces due to its own weight when lifted.
Various prior art tub constructions have been used in dragline excavating machines, all with the purpose of obtaining a high level of tub strength and rigidity. In these constructions, a tub utilizes support plates arranged to provide a rectangular grid of plates forming rectangular support compartments or trapezoidal-like compartments formed by radial and circumferentially directed plates. The instant invention is an improvement to tub constructions in which the support plate arrangement provides a number of benefits over presently known constructions.